Electrathon, Now that's thinking!! Packing tape!! Now why didn't I think of that!! Thanks!
Tree Reaper, Believe it or not, I did check the square of each side individually. Before making the cuts, I checked the length, both edges, against a straight edge and they were true. The other seam lined up perfectly.....Physically looking at the koozie, it appears that I may have made the cut for that border a fraction deeper than the rest....Would that lead to the beveling being deeper, less supporting material, more stretch/deformation??
Thanks for the input and taking the time to graphically illustrate your point!!
Troy